what happened to all the materials files?

I notice there are now main.materials.json and skin.materials.json how do these work?

EDIT: found it in the update notes

"Material files moved to new Json format, allowing multiple files for better modability"

 

there seems to always be some changes in filename structures and whatnot, certainly makes updating old mods a hell of a lot harder. Wish someone posted a guide or something dunno why information here is so scarce